Presensitized printing plates composed of an aluminum support having an aluminum oxide film on the surface thereof and a silver halide-containing light-sensitive layer formed on the support directly or over a non-silver light-sensitive intermediate layer are known, as disclosed, for example, in British Pat. Nos. 1,571,155, 1,567,844 and 1,227,603.
However, in such presensitized printing plates the formation of spots frequently occurs during the plate making process, due, presumably, to direct or indirect interaction between the metallic aluminum of the aluminum support and silver halide grains. It has further been found that this phenomenon is particularly serious in the case of a plate making process using a presensitized printing plate which has been stored under a high humidity condition for a long period of time.